Global Agenda

Interested in the game and I've seen the retail disc version going dirt cheap (probably due to its age & playerbase). I know some MMOs offer perks for those who've purchased it before and/or after they've gone F2P, is that the case here?

If the DVD is cheaper than the Steam version, then sure, go for it. The game being F2P you'll be able to use it on Steam anyway. I'd make sure the DVD comes with an activation code, though, since that's what you're after.

After the F2P came the game is split into two types of players: free agents and Elite agents. Free agents get vastly reduced loot and rewards. Elite agents get the "normal" amount of rewards (at least it was normal before F2P came). If you already bought the game before F2P then you didn't notice any difference as you were automatically Elite. Free agents had to buy the game to upgrade to Elite. So yes, the benefit to buying the game is that you get to play it at a normal speed. As a free player you would progress very, very, slowly, although you are not capped in any other ways.

Also, keep in mind you'd mostly be playing the campaigns which are reasonably fun, but the meat of the game was in the PvP, which as you've noted is not very likely due to the playerbase. So buy the game with the expectation of PvE only, but the PvE is definitely fun enough for a while. Easily worth it if it's really dirt cheap.